TWO-STAGE MAGNETIC ELECTRON MICROSCOPE PROJECTOR 343 



A commercial instrument has been completed at the RCA laboratories 

 by Zworykin, Hillier, and Vance [1941], based on the design of Marton's 

 original experimental model. A sectional view and full-scale photo- 

 graph of this instrument are shown in Figs. VIII-21a and 6. 



(a) 



(b) 



Fig. VIII-21. Sectional and external view of the RCA electron microscope. 

 This commercial model was developed in the RCA Laboratories at Camden, N.J. 

 (By courtesy of V. K. Zworykin, RCA Research Laboratories.) 



This RCA model is equipped with an electron source in the form of a 

 small tungsten filament which is partly surrounded by a guard cylinder. 

 The anode is enclosed, but the end of the guard cylinder has a hole in it 

 which is coaxial with the opening in the collimator. The full voltage 



